Method and device for conveying sheets through a printing technology machine or printer

ABSTRACT

A device for conveying a sheet through a printing technology machine or printer includes a conveying element for gripping the sheet and for moving the sheet forward. A guide plate guides the sheet and has a surface. A sensor configuration determines a location of the sheet relative to the guide plate. The sensor configuration has at least one tactile sensor element being structurally integrated with the surface of the guide plate. An actuator sets the location of the sheet relative to the guide plate. A method of conveying a sheet through a printing technology machine or printer is also provided.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to a device for conveying a sheet through a printing technology machine or printer. The device includes a conveying element for gripping the sheet and for moving the sheet forward, a guide plate for guiding the sheet, a sensor configuration for determining a location of the sheet relative to the guide plate, and an actuator for setting the location of the sheet relative to the guide plate.

The invention also relates to a method of conveying a sheet through a printing technology machine or printer. The method includes measuring an actual spacing between the sheet and a guide plate while the sheet moves continuously forward, comparing the actual spacing with a nominal or desired spacing, forming adjusting values for an actuator from the comparative values, and setting a location of the sheet with the actuator for reducing a difference between the nominal or desired spacing and the actual spacing.

In a device for conveying sheets to a pile or stack, which has become known from German Published, Non-Prosecuted Patent Application DE 43 28 445 A1, corresponding to U.S. Pat. No. 5,582,400, a sheet is held at the leading edge thereof in grippers and, moreover, is freely guided. While being conveyed, the sheet performs a fluttering movement, which is detected by an opto-electronic or ultrasound sensor. The sensor signals are converted in a control or regulating device to adjusting signals for a blast air or suction device. A particularity which exists therein is that a contact of the sheet with a guide plate is registered with the sensor and the frequency of the contacts is evaluated in a fuzzy computer. The sensors are not capable of determining with great accuracy at which locations a contact with a guide plate took place.

In a device according to German Published, Non-Prosecuted Patent Application DE 197 30 042 A1, a non-contact keying sensor is used, with which the spacing of a sheet to a reference point is registered. It is possible to provide several spacing sensors parallel to a sheet edge in order to be able to control the position of the sheet exactly with blast air or suction air. The blast air is adjusted, for conveyance to a cylinder, in such a way that the end of the sheet always lies on the shell or jacket surface of the cylinder. The contact of a sheet with a guide plate is not registered.

Furthermore, piezoelectric foils are known which are disposed on a flow body in order to register the distribution of local dynamic surface forces on a profile contour. The use of an array of piezoelectric foils on a wind channel-airfoil wing model was made public on Oct. 1, 2005 on the Internet at the address http://www.aero-tu-berlin.de/forschung/stroemungsmesstechnik/sensorik/sensorik.html. A piezoelectric foil sensor is formed of a thin PVDF-foil, which is metallized on both sides thereof. If a force acts upon the foil, a voltage change occurs, which is measured by an operational amplifier.

An impact or impingement sensor in the form of a pressure-sensitive varnish has become known from German Published, Non-Prosecuted Patent Application DE 103 17 638 A1. For example, a front hood of a passenger vehicle can be coated with regionally insulated piezoelectric varnish surfaces, so as to be able to produce a message or make a statement, where an impact or impingement signal would be produced on the front hood. In a different embodiment, the regions may be coated with differently sensitive varnishes.

According to German Published, Non-Prosecuted Patent Application DE 36 29 082 A1, foil strips with piezoelectric properties are embedded in the ground below marking strips for a field boundary of a tennis court. Upon an impact or impingement of a tennis ball in the vicinity of or on a marking strip, a signal is produced, the form of which authorizes a statement or message, as to whether the ball has struck or impacted outside the field.

A piezoelectric foil serves as a sensor for rain drops for a rain drop spectrograph according to German Utility Model DE 295 14 823 U1. Upon the impact or impingement of a drop on the foil, a voltage pulse develops, which is proportional to the pulse of the drop. The diameter and the volume of the drop can be determined from the voltage pulse. A precipitation sum per square meter results from an addition of the drop volumes.

SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide a method and a device for conveying sheets through a printing technology machine or printer, which overcome the hereinafore-mentioned disadvantages of the heretofore-known methods and devices of this general type and which detect an impact or impingement against a guide plate when conveying a sheet, with simple and cost-effective equipment.

With the foregoing and other objects in view, there is provided, in accordance with the invention, a device for conveying a sheet through a printing technology machine or printer. The device comprises a conveying element for gripping the sheet and for moving the sheet forward. A guide plate guides the sheet and has a surface. A sensor configuration determines a location of the sheet relative to the guide plate. The sensor configuration has at least one tactile sensor element being structurally integrated with the surface of the guide plate. An actuator sets the location of the sheet relative to the guide plate.

In accordance with another feature of the invention, the tactile sensor element is disposed at a side of the guide plate facing towards the sheet.

In accordance with a further feature of the invention, the tactile sensor element is constructed as a piezoelectric foil.

In accordance with an added feature of the invention, the tactile sensor element is constructed as a piezoelectric varnish.

In accordance with an additional feature of the invention, a plurality of the tactile sensor elements are disposed in raster- or screen-shaped partial surfaces on the guide plate.

In accordance with yet another feature of the invention, the device includes a temperature sensor associated with the tactile sensor element.

In accordance with yet a further feature of the invention, the device includes at least one non-contact operating spacing sensor associated with the tactile sensor element.

In accordance with yet an added feature of the invention, the actuator encompasses air flow-through openings formed in the guide plate.

In accordance with yet an additional feature of the invention, the device includes a plurality of sensor elements, and at least one charge transfer element. The plurality of sensor elements are connected to the at least one charge transfer element.

In accordance with another feature of the invention, a plurality of sensor elements are selectively provided for signal evaluation.

In accordance with a further feature of the invention, for temperature compensation, a plurality of the tactile sensor elements are respectively disposed in a bridge circuit.

With the objects of the invention in view, there is also provided a method of conveying a sheet through a printing technology machine or printer. The method comprises measuring an actual spacing between the sheet and a guide plate with a plurality of spacing sensors while the sheet moves continuously forward, to produce actual spacing signals. The actual spacing is compared with a nominal or desired spacing to form comparative values. Adjusting values for an actuator are formed from the comparative values. A location of the sheet is set with the actuator for reducing a difference between the nominal or desired spacing and the actual spacing. A contact signal is produced if the sheet contacts the guide plate. The actual spacing signals are weighted in dependence on the contact signal.

Thus, according to the invention, the surface of a guide plate is provided with at least one tactile sensor element. It may be reliably determined with the sensor element whether and where a sheet rests on the guide plate. An actuator can be set by the sensor signal to act upon the sheet, so that the sheet and a succeeding sheet respectively assume a desired position with respect to the guide plate.

A guide plate surface or guide plate partial surfaces may receive a piezoelectric layer, whereby local segments of the guide plate surface are electrically contacted. The guide plate surface and the tactile sensor elements form a mechanical unit. Due to the provision of a plurality of guide plate partial surfaces with a respective sensor element, it is possible to select the respective sensor elements used for the evaluation, according to the particular application. The selection of the active sensor elements may be effected by servicing personnel or may be computer-controlled. If pneumatic actuating elements are disposed in a guide plate, there then results a spatially close coordination between sensor element and actuator element. A piezoelectric varnish or a covering of piezoelectric foil is installable on a guide plate as a tactile sensor element. If a signal arises on a sensor element due to impact or impingement of a sheet, the signal can then cause a change in machine parameters, such as the feed rate of blast air, in order to prevent an impact or impingement in the future. In order to reduce temperature errors, the temperature on the guide plate surface can be measured routinely, and a blast air or suction air device can be used for the adjustment.

When using a plurality of sensor elements, it is advantageous to store the signals in accordance with the principle of a load or charge-shifting or transfer element and to read it out in a time-controlled manner. In order to control the level of flight of a sheet with respect to a guide plate, tactile sensor elements can be used in combination with ultrasound sensors. It is thereby, for example, possible to regulate the flight level in the vicinity of the freely guided trailing edge of the sheet. If, for example, a spacing measurement signal of the ultrasound sensor lies in a prescribed region and a tactile sensor indicates a contact of the sinuous or undulated sheet with the guide plate, the blast air rate in the contact region can then be increased.

In accordance with the method of the invention, when using a plurality of spacing sensors, a signal is produced, if a sheet contacts a guide plate. Depending upon the signal, actual spacing signals between sheet and guide plate are evaluated, which are determined with the spacing sensors.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is illustrated and described herein as embodied in a method and a device for conveying sheets through a printing technology machine or printer, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partly schematic and partly top, front and side perspective view of a device for conveying a sheet along a guide plate;

FIG. 2 is a cross-sectional view through a guide plate with superficial guidance of signal lines; and

FIG. 3 is a cross-sectional view through a guide plate with signal lines passing through the guide plate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the figures of the drawings in detail and first, particularly, to FIG. 1 thereof, there is seen a sheet 1, which is held at the leading edge 2 thereof in grippers 3 of a gripper system or conveying element 4. The sheet 1 is moved with the gripper system 4 in a conveying direction, represented by a horizontal arrow 5, along a guide plate 6. The guide plate 6 contains a number of nozzle openings 7, which are respectively connected to a blast air device or actuator 8. Furthermore, piezoelectric sensors 9 are disposed on the guide plate 6 and are connected to a control and regulating device 10. The nozzle openings 7 and the piezoelectric sensors 9 form a screen or grid or raster with alternating occupancy along the lines of a chessboard pattern. Blast air rates through the nozzle openings 7 are individually adjustable. In the plane of the piezoelectric sensors 9, a temperature-detecting element 11 is disposed on the guide plate 6 and is connected to the control and regulating device 10 as well. Spacing sensors 12.1, 12.2 and 12.3 which are set into the surface of the guide plate 6 are connected to the control and regulating device 10, permitting the measurement of the spacing between the sheet 1 and the guide plate 6.

Due to the fact that the sheet 1 is held only at the leading edge 2 thereof and is otherwise freely guided, contact may be made with the guide plate 6 upon an incorrect adjustment of the blast air rates. Should the sheet 1 contact the guide plate 6 in a particular region, contact signals are produced at the piezoelectric sensors 9 lying in the region, and are processed in the control and regulating device 10. The signals of the piezoelectric sensors 9 are stored in load or charge transfer or shifting elements 9′ and evaluated in the control and regulating device 10. The signal strengths of the piezoelectric sensors 9 are a measure for the contact forces between the sheet 1 and the guide plate 6. Regulated outputs or variables for the blast air device 8 are calculated from the signals of the piezoelectric sensors 9 and the spacing sensors 12.1, 12.2 and 12.3. The blast air device 8 is controlled in accordance with the location of the contact with the guide plate 6 and the course of the spacing of the sheet 1 to the guide plate 6, in such a way that no further contact of the sheet 1 and of a following sheet 1, respectively, takes place with the guide plate 6, and the spacing of the sheet 1 lies within a prescribed tolerance range. The signals of the piezoelectric sensors 9 are very temperature-dependent. The processing of the signals of the temperature-detecting or sensor element 11 permits a temperature-dependent correction of the adjusting signals of the blast air device 8.

A more detailed construction of the guide plate 6 is provided in the sectional view of FIG. 2. The guide plate 6 is formed of a base plate 13, whereon the piezoelectric sensors 9, in the form of rectangular-shaped piezoelectric varnish surfaces 14, are applied. Signal lines 15 run in free spaces between the piezoelectric varnish surfaces 14, and lead to the control and regulating device 10. The piezoelectric varnish surfaces 14 and the signal lines 15 are covered by an elastic protective varnish 16.

In a different embodiment according to FIG. 3, signal lines 17 respectively contact a piezoelectric varnish surface 18 on the side facing away from the sheet 1. Borings 20 for guiding the signal lines 17 are formed in the base plate 19 of the guide plate 6. The signal lines 17 connect the piezoelectric varnish surfaces 18 to the control and regulating device 10. As in FIG. 2, the piezoelectric varnish surfaces 18 are sealed with an elastic, ink-repellent protective varnish 21.

This application claims the priority, under 35 U.S.C. §119, of German Application DE 10 2005 024 992.2, filed Jun. 1, 2005; the prior application is herewith incorporated by reference in its entirety. 

1. A device for conveying a sheet through a printing technology machine or printer, the device comprising: a conveying element for gripping the sheet and for moving the sheet forward; a guide plate for guiding the sheet, said guide plate having a surface; a sensor configuration for determining a location of the sheet relative to said guide plate, said sensor configuration having at least one tactile sensor element being structurally integrated with said surface of said guide plate; and an actuator for setting the location of the sheet relative to said guide plate.
 2. The device according to claim 1, wherein said at least one tactile sensor element is disposed at a side of said guide plate facing towards the sheet.
 3. The device according to claim 1, wherein said at least one tactile sensor element is constructed as a piezoelectric foil.
 4. The device according to claim 1, wherein said at least one tactile sensor element is constructed as a piezoelectric varnish.
 5. The device according to claim 1, wherein said at least one tactile sensor element is a plurality of tactile sensor elements disposed in raster-shaped partial surfaces on said guide plate.
 6. The device according to claim 1, further comprising a temperature sensor associated with said at least one tactile sensor element.
 7. The device according to claim 1, further comprising at least one non-contact operating spacing sensor associated with said at least one tactile sensor element.
 8. The device according to claim 1, wherein said actuator encompasses air flow-through openings formed in said guide plate.
 9. The device according to claim 1, further comprising at least one charge transfer element, said at least one tactile sensor element being a plurality of tactile sensor elements connected to said charge transfer element.
 10. The device according to claim 1, wherein said at least one tactile sensor element is a plurality of tactile sensor elements selectively provided for signal evaluation.
 11. The device according to claim 1, wherein said at least one tactile sensor element is a plurality of tactile sensor elements disposed in a bridge circuit for temperature compensation.
 12. A method of conveying a sheet through a printing technology machine or printer, the method comprising the following steps: measuring an actual spacing between the sheet and a guide plate with a plurality of spacing sensors while the sheet moves continuously forward, to produce actual spacing signals; comparing the actual spacing with a nominal or desired spacing to form comparative values; forming adjusting values for an actuator from the comparative values; setting a location of the sheet with the actuator for reducing a difference between the nominal or desired spacing and the actual spacing; producing a contact signal if the sheet contacts the guide plate; and weighting the actual spacing signals in dependence on the contact signal. 